1. Field of the Invention
The present invention relates to an imaging device suitably incorporated within an electronic equipment such as a portable telephone, a personal digital assistance and a notebook personal computer, and an electronic equipment incorporating therein the imaging device. More particularly, it relates to an imaging device capable of imaging both surrounding distant views such as a landscape and a person, and close views such as a fingerprint and a validating signature, and an electronic equipment incorporating therein the imaging device.
2. Description of the Related Art
Some electronic equipments such as a portable telephone, a personal digital assistance and a notebook personal computer incorporate therein an imaging device for capturing the image of the surroundings such as a landscape and a person. Furthermore, for purpose of prevention of leakage of information stored within an electronic equipment and identity verification of a person seeking authentication at an electronic business transaction, an electronic equipment is required to incorporate therein a device for capturing a user's fingerprint as an image to verify a person seeking authentication.
Conventionally, an electronic equipment has been known which is capable of capturing both the image of distant views (hereinafter, referred to as the surroundings) such as a landscape and a person, and the image of close views such as a fingerprint or the like (hereinafter, referred to as a fingerprint) using the same image pickup device. Such an electronic equipment includes two independent focus optical systems therein and is configured to mechanically select a focus optical system that should receive light and deliver light from the surroundings or a fingerprint to the image pickup device. Particularly, for a portable electronic equipment whose volume and manufacturing cost of device are considered relatively critical, achieving the ability to image the surroundings such as a landscape and a person, and in addition, verify a person seeking authentication via a fingerprint by using the same image pickup device has a large meaning.
Japanese Patent Application Laid-open 2001-142606 discloses an example of such kind of electronic equipment. FIGS. 1A and 1B respectively are a front view and a cross sectional view of such conventional electronic equipment, showing operation for imaging the surroundings. FIGS. 2A and 2B respectively are a front view and a cross sectional view of such conventional electronic equipment, showing operation for imaging a fingerprint. As shown in FIGS. 1A and 1B, the electronic equipment is a portable telephone having a surroundings imaging lens system (hereinafter, it represents a lens system for imaging the surroundings) 102, a switch section 105 and a finger rest prism (hereinafter, it represents a prism on which a finger rests) 106 made of a transparent material, all of which are provided in a housing 104. A mirror 103 is mounted in the switch section 105 that is made to slide in left or right direction to switch imaging modes.
The finger rest prism 106 has a finger rest face 106a facing the outside of the housing 104 and a prism bottom face 106b formed opposite the finger rest face 106a, and a reflecting face 106c and a lens system fixing face 106d are formed between the finger rest face 106a and the prism bottom face 106b. Within the housing 104 are provided an image pickup device 101 such as a CCD, a fingerprint imaging lens system 107 and a display 108 such as a liquid crystal display, and the display 108 is disposed to face the prism bottom face 106b, and further, the fingerprint imaging lens system 107 is fixed to the lens system fixing face 106d. When the switch section 105 is positioned on one side out of the two sides, light from the surroundings is focused onto the image pickup device 101 passing through the surrounding imaging lens system 102. In this case, the switch section 105 is positioned so as to make the mirror 103 positioned outside a light path. Furthermore, when the switch section 105 is positioned on the other side, light incident on the finger rest prism 106 passes through the fingerprint imaging lens system 107 and is reflected by the mirror 103 to thereby be focused onto the image pickup device 101.
The operation of the electronic equipment for imaging the surroundings will be described below. As shown in FIG. 1A, when the switch section 105 is made to slide to the right side in the figure, light from the surroundings is collected by the surroundings imaging lens system 102 and focused onto the image pickup device 101, as shown in FIG. 1B. Thus, the image of the surroundings is captured by the image pickup device 101. Thereafter, the captured image of the surroundings is displayed on the display 108 and then, the captured image can be viewed from outside since the finger rest prism 106 is made of a transparent material.
Subsequently, the operation of the electronic equipment for imaging the fingerprint will be described below. First, as shown in FIG. 2A, the switch section 105 is made to slide to the left side in the figure. Then, as shown in FIGS. 2A and 2B, a finger is made to tightly rest on the finger rest face 106a of the finger rest prism 106. Keeping this state of the finger, the display 108 is made to uniformly emit light and the finger tightly resting on the finger rest face 106a is illuminated. The light scattered by the finger is reflected by the reflecting face 106c of the finger rest prism 106 and passes through the lens system fixing face 106d and further the fingerprint imaging lens system 107, and then, is reflected by the mirror 103, and finally is focused onto the image pickup device 101. After the image of the fingerprint is captured by the image pickup device 101 as described above, the captured image is displayed on the display 108 and then, the captured image can be viewed from outside since the finger rest prism 106 is made of a transparent material. Furthermore, since the display 108 can show a graphic symbol indicating a profile of the finger and a message, for example, “Put a finger here” when a fingerprint is imaged, a user is able to put his/her finger on a previously determined position and therefore, the imaging device is securely able to image a specific portion of the fingerprint.
As described above, the conventional electronic equipment disclosed in Japanese Patent Application Laid-open 2001-142606 has two focus optical systems therein respectively for imaging the surroundings and a fingerprint and is configured to mechanically switch lights respectively passing through both systems so as to allow one of the lights to pass through one of the two focus optical systems to deliver the corresponding light to an image pickup device, thereby enabling the equipment to capture both images of the surroundings and a fingerprint using the same image pickup device.
It should be noted that the inventors of this application developed an optical system named “SOFI (Single Optical Fiber Imaging” in the past and disclosed it in the publication “NEC TECHNICAL JOURNAL Vol. 51, No. 10 pp. 90-95 (1998) ‘Development of a pen-shaped scanner and its applications’.” The SOFI optical system has been developed to realize a hand-held scanner configured to trace a document and input the corresponding data to a computer.
The SOFI optical system has a light source, a glass substrate, an image sensor and an optical fiber array. The glass substrate is disposed in a location on which light from the light source is incident. The image sensor is disposed on a surface of the glass substrate opposite the surface thereof that faces the light source. And the optical fiber array is provided to face the image sensor. The image sensor has a window being passed light through and a plurality of pixels. The optical fiber array has a plurality of optical fibers. And the light from the light source transmits through the glass substrate and the window to enter the plurality of optical fibers.
The SOFI optical system operates as follows. First, a document to be read is made in contact with the optical fiber array and keeping this state of the document, the light source is made to emit light. Light emitted from the light source transmits through the glass substrate, the window formed on the pixels and the optical fibers in this order to illuminate the document. Light reflected from the document enters the optical fibers through which the illumination light has transmitted and then, enters the image sensor. Thus, the SOFI optical system acquires the image of the document. Although the SOFI optical system has been developed for reading a document, it may also be used as an imaging device for imaging a fingerprint.
However, the above-described conventional technique includes the following problems. First, the electronic equipment disclosed in Japanese Patent Application Laid-open 2001-142606 includes components having a large volume therein for imaging an object and therefore, the equipment is forced to increase its volume. That is, the above-described conventional electronic equipment has two independent focus optical systems provided therein each for imaging the surroundings and a fingerprint, and therefore, distances needed to focus the respective images onto the image pickup device have to individually be secured between the corresponding lens and the image pickup device. In addition, in order to switch the two focus optical systems, the electronic equipment needs physical space for making the switch section slide in left or right direction to switch imaging modes. As is mentioned above, the electronic equipment disclosed in Japanese Patent Application Laid-open 2001-142606 is unfavorably forced to increase its volume.
Secondly, the electronic equipment disclosed in Japanese Patent Application Laid-open 2001-142606 is configured to make a user view the display through the finger rest prism. Therefore, the user feels it difficult to view a displayed image since the image is deeply located behind the prism. In addition, when capturing the image of fingerprint, oil on a finger surface adheres to the finger rest prism, deteriorating the image to be displayed. As described above, the conventional electronic equipment includes the drawbacks. That is, a user forcibly feels the image displayed on the display is deeply located within the equipment and the residual fingerprint image left on the finger rest prism deteriorates the image to be displayed.
Thirdly, when capturing the image of the surroundings such as a landscape or a person, it is desirable to be able to capture the image of the surroundings in a number of directions in which the electronic equipment is moved regardless of orientation of the electronic equipment. However, since the above-described conventional electronic equipment has the focus optical system fixed to the housing of the equipment for imaging the surroundings, the equipment is able to image an object only in one specific direction in which the equipment is aimed. As described above, the conventional electronic equipment includes the problems. That is, degree of freedom in selecting directions in which the equipment is moved to capture the image of the surroundings is small.
Furthermore, the above-described imaging device employing SOFI optical system therein includes the problems. That is, although the imaging device is able to capture the image of fingerprint, it is not able to capture the image of the surrounding.